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Thursday, April 12, 2007

Is time an illusion?

Nah, I am not going to answer this question. (Actually, I am not really sure what this question means. You can ask me if I think time is a dimension, then I'd say yes.) I just read this discussion of the question that Wired lists as the second on its list of 'big questions' (another one is 'Why is fundamental physics so messy?'). I just thought it might humor you what people had to say about it. It seems if we'd take a vote on it, the majority believes time is an illusion. Feel free to let me know your opinion.

From the comment section:

Roberto: The unidirectional time in the equations of physics is constructed from the original, circular time.

(now that explains everything)

Guest: does time really exist? Not in the least. Time is a construct. Created by mankind to assert ourselves over the other dimensions. We have freed ourself from the laws of physics and created a new prison, time. (Gee, I didn't even notice we freed ourselves from the laws of physics. That's what can happen if you live in a small city in west Ontario - someone could have told me!)

Guest: if you ever get the opportunity, use DMT (dimethyltryptamine). you will see far beyond the illusion of time and realize many things that cannot be expained.(Fat chance)

Guest: Time is an invention of convenience. Kind of like x^^0 = 1 .

(Aside: this is not an invention of convenience but a consequence of smoothness)

Guest: It's a tautological question. Time is what's measured by a clock, just as intelligence is what's measured by an IQ test.

(Comes back to the point that the question, as formulated, is essentially empty.)

Eric: Human sentience requires this illusion to give us the illusion of free will.

Robert: there is no such thing as time, instead it should be thought of as the cycle of mater and energy from light to total entropy to highly energized quantum materials which all together form the macro world

(thats what happens if you 'think horizontally')

Pierre: If we are going to think about time, shouldn't we first ask ourselves "are thoughts real?".

(I link therefore I am).

Jeff M: It doesn't matter - the question is moot.

(Thanks to Jeff M for enriching my vocabulary, I agree. Will try to use 'moot' from now on instead of 'nonsense'.)

pachorazy: if we change our perception of time can we change how fast we age?

(and how do you measure 'fast' if not with 'time'?)

Stuart: I suppose that it does not matter. Time is how we perceive it. What it may theoretically be has no effect on how it IS for us. So... it is what it is.

letibenson: Time is an allusion and here is why-- our congress can tell us when we need to set our clocks forward or back by an hour. If time was real it would be out of there hands

tculp: If we break down the question, we have an initial question - what is illusion?

Time flies like an arrow, fruit flies like a banana. (From the book "Instant Physics")Alex: Time is a man-made idea, it is a construct of human society used to make life more convenient and easy.

Gary: It might be time to go back to the Greek philosophical definition of the universe and work our way forward again.

(have fun, say hello if you arrive in the 21st century)

Robert: the fascination that many people have these days with wanting to believe that everything happens all at once, there really is no time.

JD Bailey: Time is not an illusion. Time is a multidimensional relationship.

Jim: Life is illusion and time comes from life.

Ric: One of the secrets of TIME, which I have realized, is that TIME itself is the constant we call “infinity”.

Absent time particle physics would not need four-vectors. Absent homogeneous time mass-energy would not be conserved. Absent oscillators as clocks use radioactive decay.

Standardized tests neither guarantee success nor exclude failure. However, diamonds are not the default in kimberlite and lamproite - they must be diamondiferous. Cornell University abuts a kimberlite dike. Cornel solicits alumni donations not grease tables' output. Testing to remove 90% of the dross is better than diversity to remove 90% of the value.

Professional managment is about process not product. We are not sane to the extent that our thoughts are humane - not in a production environment! Charity is a byproduct of surplus not a State mandate.

I refuse to be "hypnotized" by any illusionist that dangles a clock in front of my eyes!

Even "hypno/therapists" know time is an illusion?..they use this fact to extort vunrable persons into devulging their personal problems over long periods, at extortionist prices?..time is money they say, they also state: my hasnt time flown?..eh..that will be an extra 20 dollars, with a gleaming ;) of course.

Keep your gold..silver or any other monies..time is the most valuable comoddity (commercial oddity ) there is .

One reason I do not own a watch, I am not a slave for time.

Seriously, time is an illusionary weapon, thrusted upon us because of our ancestors mystical need to measure and watch things in motion.

If you take time out of every equation mathematically created, lengths, distance and motion would become obsolete?

Time is no illusion for reality, it's a neccesary consequence of awareness.

There are serious physicists who believe that time does not exist: Julian Barbour is an example.

But I agree that it's not quite clear what one means when one says that time does not exist. If one takes a purely instrumental view of science, then time is just a useful tool for describing the phenomena we observe, so it wouldn't really make sense to say that it doesn't exist. Barbour, I think, does give a clear explanation by what he means by time not existing, but it's been a long time since I read his book.

yeah, I believe one can make more sense out of this question if one formulates it more carefully. I personally find it more interesting to ask why we have something like a time at all. The question whether time is an illusion does imho include too many other unknown realms, e.g. what is consciousness, how do our observations influence 'reality', is there such a thing as a 'reality', do we share a common reality, etc etc. Makes a nice topic for a dinner party, but I wouldn't want to write a PhD thesis about it.

Kea, since I don't understand 'time' there are probably people who understand it better. I have some sympathy for the idea that time is emergent - I wouldn't say this is the same as saying 'time is an illusion'. I am not aware I was mocking anybody specifically. I am sorry if you feel offended by what I found entertaining. Best, B.

Time taken as a dimension has another unique characteristic besides its direction (arrow of time). The other (space) dimensions are available to perception in all their extent, while for the dimension of time there is only one point available, the present moment.

To appreciate the difference, if time was like the other dimensions, one would be able to "look" in one direction and see all the past moments of the point of space on which he/she stands, and "look" in the other direction and see all its future moments.

So in this sense we resemble the Flatlanders of a 2 dimensional world who can only see one slice of a 3D object, its intersection with the plane of their world. We are Flatlanders as regards time.

And maybe that is what makes a lot of people say that time is an illusion. Maybe they sense that time also has an extension like the other dimensions, and that past and future moments have some kind of existence, but we only perceive one slice of it "at a time", the intersection of the time dimension with our 3D space as it moves along its length, what we term the present moment.

There is a trivial answer to the question "what is time?" which is "time is what's measured by a clock". But this definition is not as empty as it seems: The non-trivial part is that if you have two (or more) clocks they tend to agree on how much time passed if calibrated correctly and both working properly. Thus the amazing property of time is that it seems to exist away from an individual clock used to define it and thus it makes sense to measure it.

This is a bit like the 0th law of thermodynamics which states "temperature exists" in the sense that in equilibrium there is a unique, homogeneous temperature.

I agree with the consensus that Time a complex function, and it can of course play tricks upon the mind, and memory?

As a recent example, I was walking my sisters canadian dog (the small one with the huge underbite my linked site), along the beach here in the UK.

It was a glorious evening, I was thinking about a scientific article I had read earlier, the dog ( celti ), was running around oblivious to my concerns. Anyway, I suddenly realised the moment was really special, in this case I was feeling great, and celti was similarly so. When we arrived back home, I sat down to revise the article I was thinking about, and could not help thinking about the walk on the beach, my mind was trying to "return" to the beach?

I looked down to celti, who was sleeping fast, then his legs started to move and twitch, and I could see by this that he was dreaming, he was "running" around in his sleep!..I wondered if his "mind" was experiencing a similar effect as mine, special event memory?..was he running back to the beach?..or actually on the beach?

What I thought was interesting was the fact that celti enjoyed his experience, and could replay this event in his sleep?..just as I could relish the moment in thought, as a memory, time obviously could influence my sisters dog into a sleep related experience?..to the extent of his mouth curling up, as if he was grabbing at the stick I used to play fetch with.

Whilst I could not replay events via memory 100%, (to do so would be not a past_tense event, I would not be able to comprehend a "now")..much like the quote Bee provided by Wheeler..my memory of the time was not sufficient enough to create the event 100% over and over? for that you need the "now_time" as one off event experience.

Julian Barbour, if my memory serves me correct, was adamant that "time" could be struck out of QM, and therfore open the door to solutions in QM as a a fundamental superior model to Relativity?

Even if one removes all timepieces from the external world, one cannot escape the inherent internal "mind" clock that provides the conscious observer with memory of events past.

Also, without time, I could remember the future (forcefully of course, this is illusionary), and if I was the type of person to force this upon others, I would be comparable to a mordern day soothsayer?..voodooist?..or prophet?

It makes you wonder though (or at least it makes me wonder) about the "thickness" of the time slice of our world. We do not perceive a little bit of the past and a little bit of the future along with the present, we only perceive one moment, now. So does that mean that this thickness is equal to one Planck time, i.e. that there is a minimal time scale? Is a minimal time scale the same thing as saying that time is quantized? Would a quantized time explain a lot of other quantized phenomena, perhaps all? This idea looks very promising. Has anyone done anything along these lines? I think Fotini has worked on this. Has she come up with anything interesting?

I suspect this question became popularized mainly due to Julian Barbour, specifically his popular books. I think he has in mind a more or less concrete problem in canonical quantum gravity, though I never familiarized myself with this...if you are interested you should ask Lee.

Here and elsewhere in science, as stressed not least by Henri Poincare, that view is out of date which used to say, "Define your terms before you proceed." All the laws and theories of physics, including the Lorentz force law, have this deep and subtle character, that they both define the concepts they use and make statements about these concepts....Any forward step in human knowledge is truly creative in this sense: that theory, concept, law and method of measurement - forever inseparable - are born into the world in union."

___

Thus, time is what is measured by a clock, and a clock is what measures time. A good clock measures time so that motion is simple.

___

Also, taking the obligatory dig at you-know-what, since string theory does not give us any method of measurement of anything, it is not a forward step in human knowledge, by the above yardstick.

yes, I always liked this quotation, I think it hits the point. Regarding quantization, it seems to me you are mixing up two different things. 'quantizing' doesn't mean the thing quantized comes in quanta. What can come in quanta are its eigenvalues. Like e.g. energy eigenvalues. In a non-compact space, eigenvalues of the position operator are not quantized. There's no reason to assume time comes in 'quanta' (neglecting the question what the meaning of an time operator might be).

Now you can argue that the Planck length is a minimal length, but this doesn't mean position eigenvalues become discrete. Instead, you'd expect it to be a limit on what resolution of distances are possibly achievable. Likewise, you can understand this for a timelike direction as a fundamental limit on how precisely one can possibly measure 'when' an event took place. Reg. Fotini, check on SPIRES, I don't know more.

Hi Moshe,

well, I was hoping for a three sentence summary...

Hi Arun,

World in union. I like that. We were just making fun out of MTW. I wonder if there is anybody in the world who is able to find in this book what he is looking for, and whether the impossibility of this endeavor was on purpose by the authors. Best,

Stefan, or Sabine, since most of the time you think, I have a question about time.It would seem that 3+1 space-time is just that, a space-time dimension (one thing).

For anything existing in 3+1ST , without time, ‘space‘ would become meaningless, and the converse. If one visualizes space as a 3d grid of any shape, the distinction between any 2 points, A and B, on the grid only has meaning if time is used as a measure between them. If the time is zero, then there is no way to know that A is different than B. In order to make the measure A to B, one would count the time somehow and it would be a positive value. To measure back from B to A, the space ‘direction’ would change but the ‘time’ value would remain positive. If the time direction changed, then the trip A to B to A would occur in zero net time and therefore one couldn’t make the spatial distinction between A and B.

I am not sure what your mathematical knowledge is. You can define a distance (via the metric) between two points, even if there is no such thing as a time, i.e. all dimensions are spacial (no matter how many) - you are used to that from Euclidean geometry.. The existence of such a distance measure is a condition that is usually required of the space-time we are living in (it seems to go with our experience). Does that help?

Salvadore Dali has a "warped sense of time" when it comes to time pieces? :)I mean with the tesserack, he may of thought there was some "higher dimensional attribute" to religion?

Killing Time

Barbour posits that time is, in fact, an illusion - a measure imposed on the world by humanity. He explains this with the concept of a 'now', which he describes as a snapshot in time - a completely frozen, self-contained instant (much like a Polaroid photograph). Time is simply the measure of the space between two separate and unrelated 'nows.'

1. Absolute, true, and mathematical time, of itself and from its own nature, flows equably without relation to anything external, and by another name is called "duration"; relative, apparent, and common time is some sensible and external (whether accurate or unequable) measure of duration by the means of motion, which is commonly used instead of true time, such as an hour, a day, a month, a year.

2. Absolute space, in its own nature, without relation to anything external, remains always similar and immovable. Relative space is some movable dimension or measure of the absolute spaces, which our senses determine by its position to bodies and which is commonly taken for immovable space...

Of course this isn't a fashionable viewpoint now, but it was the basis for the preferred-frame special relativity of Lorentz and Poincare. That makes the same predictions as Einstein's. The latter seems more democratic, since it doesn't have any preferred frames or absolutes. But it has the drawback that, to make time fully interchangeable with space, you need a bidirectional time -- even though our experience, thermodynamics, and quantum mechanics seem to demand one-way time. (See Ilya Prigogine's The End of Certainty.)

One solution, used in parameterized quantum field theories, is to take Minkowski space-time and throw in an additional one-way Newtonian time. With Lorentz/Poincare relativity, you automatically get that one-way parameter, using only one time. Lorentz and Poincare stuck to their guns, and never bought into Einstein's theory. But only he found a working theory of gravity.

Is there really such a thing as absolute time and space? Newton said yes. Take a bucket of water, hang it from a rope, and spin it. The concave surface of the water tells you it's turning with respect to an absolute space.

Leibniz, and later Mach, said no. If you took all the objects in the universe and turned them around with the bucket, the water would lay flat. I think Einstein saw Mach's principle as a way to fix an ugly inconsistency in his version of special relativity. While that has no preferred frames for linear motion, it still has a preferred frame for rotation. In his general relativity, you chalk that up to gravitational interaction with the other objects in the universe, rather than an absolute space.

Now we have an experimental test of Einstein's idea, Gravity Probe B. It was a gyroscope in polar Earth orbit. Just as general relativity says the rotation of masses around Newton's bucket should affect the water, Earth's rotation should have affected this gyroscope. (I have a quantum-mechanical gravity theory based on Lorentz/Poincare relativity which says it didn't.)

Anyway, speaking of time, it's running out! The preliminary results from Gravity Probe B are scheduled to be announced Saturday, at a meeting of the American Physical Society.

Or the two could be one and the same. As strange as it sounds, in curved spacetimes there is necessarily such a thing as a "rate of propagation of time", which is equal to c.

In a flat Galilean spacetime c can be considered infinite, and time also has an infinite rate of propagation: that is all points of space have the same (proper) time coordinate, and this coordinate changes simultaneously for all of them, which amounts to an infinite rate of propagation of time.

In a curved spacetime, the points of space have different (successive) proper time coordinates, and as t changes these coordinates change successively so that a point with proper time t' moves away from as at the speed of light. Which can be seen as a rate of propagation of time that is equal to the speed of light.

So maybe the reason c functions as an upper speed limit, and so many strange phenomena appear as a body approaches this speed, is that it is the rate of propagation of time, and it just happens that light is the only thing that can reach this limit.

Nothing would move. No movement. No time. Death is the only true stopping of movement and time. Sorry if this isn't scientifically complex enough, but some things aren't really all that complex. ;-)

It's only our *perception* of time that varies, but it just keeps on keeping on whether we notice or not. I think this goes along with questioning whether or not there is an "External Reality."

And I don't intend to offend anyone, but it's these kinds of questions that "common" people find rather silly and indulgent. When most people hear that scientists are spending so much *time* and *money* ;-) on such questions it only makes them that much more skeptical of any good that science might offer. Not that I believe these things. I'm just reporting from the field, so to speak. ;-)

well. I was hoping to communicate that we actually don't spend time on that question... See, the question whether 'time is an illusion' isn't something physics can answer. To begin with, the question isn't well posed because its not clear what an 'illusion' is. But it seems the term 'illusion' is somewhat connected to the human consciousness. I have no doubt that we all perceive time somewhat different, and different in various circumstances, maybe one can understand some of the reasons for that etc etc, but that's got nothing to do with the question whether time is 'emergent', or why it seems to 'point' into one direction and not into the other. The latter two are question you can ask precisely and try to answer within physics. Everything that includes a notion of consciousness, what we perceive as reality etc etc, gets somewhat fuzzy and vague. Its definitely interesting, but unless one asks a precise question one can't scientifically do very much about it.

"How would you know if time stopped?"

Nothing would move. No movement. No time.

But since you wouldn't move as well, you wouldn't notice. Think about stopping a movie and then continue. It doesn't change anything about the movie. I think you are referring to 'time' not as something we all share, but you think of 'stopping' it only for one person or such?

thanks for the link. Ouch. Is is really that bad? I have never been there. Regarding illusions, you have a point. At least Bank of America has decided today that my money is an illusion. I am seriously pissed off, at least they could stop sending the account statements in Spanish, since I don't speak Spanish. Anyway, have a nice day,

of course that it is not that bad, it is not bad at all, especially not today, 17 years after communism. The clip is green propaganda but it is well-created propaganda.

Most of these discussions about time stopped are valuable through their entertainment value. In physics, one must simply have some description of reality as a function of time (in GR, it can be any coordinate, in S-matrix quantum gravity, one only distinguishes asymptotic past and future).

If a picture of physics is consistent with this normal understanding of time, everything is determined and additional words are just poetry.

If someone wants to create a picture where time plays a different role than above, he or she should first settle what the new conceptual and mathematical framework is - otherwise all discussions are bound to be ill-defined

Hi Bee, these are very good questions but they're unlikely to be answered before the full framework emerges.

Euclidean spacetime is now just a trick to make calculations - an analytical continuation of Minkowski physics.

In the Minkowski space, one must first have a system of asking questions - you have initial conditions at t1 and ask what are the probabilities at t2.

I find it obvious that the same framework with time becoming Euclidean is impossible because causality can't be defined here. The Minkowski space has the feature that the timelike cone is disconnected into its past and future component. No such disconnect exists in Euclidean spacetime, preventing us from any causal interpretation of events in it.

On the other hand, near the Big Bang, when the questions about the very initial conditions of everything are asked, or in other singularities, it may turn out to be important to put fluctuating signature etc. into the picture. That's the Bogdanoffs' project - promoting these things would be another fun. ;-)

The DDR and Czechia developments with environment must be analogous. The main difference is that Czechia didn't have a rich Western brother to pump a lot of money into it which may have been a good thing, after all (even though Western Bohemia was freed from Nazis by the US army which didn't matter after all).

This pumping of money into DDR was counterproductive and increased inefficiencies and frustrations of all kinds.

The uselessly heavy communist industry of DDR and CSSR disappeared. People literally thought that the more coal/steel they produce, the stronger countries we would be. We no longer think like that.

Lots of things became efficient and environmental just by eliminating the irrational pressure to make them different. But many things that are today are economically justified and making them much more environmental is probably counterproductive again.

It's the market that decides best about the balance between clean environment and the degree of masochism.

From the perspective of a photon/graviton, there is no time, and thus no space. From the perspective of massive matter, there is space, and the illusion of time is created from the different arrivals of photon/graviton from space. Time appears to have a direction because matters interact towards greater chaos from an implied initial state of perfect order. What is the composition of perfect order, how can it exist under an implied 'zero' space, and how that came into being, of course, are the great questions.

Classically: Time is the 't' in the equations of motion, and motion is defined as change of position in space, which seems to have a more tangible meaning for us. We can solve for t and if it works well, we call that a clock.

Quantum Mechanically: Time is the 't' in the Schroedinger equation (or in the Heisenberg picture if you believe Dirac). We can also solve for 't' in here too, although in more amusing ways. Space stays as we think it does, much *easier* concept we encounter very early in our lifes.

Caveat: Add gravity to the quantum (or add quantum to the (space)time), and the notion of *observables* becomes a bit tangled. In this case finding the 't' is also part of the problem....(of time), cus it turns out it is also a *dinamical variable*. [This is btw also a problem in classical GR, although not as harmful as in the quantum realm.] This opens up a box of possibilities to what to call *time*, but the idea stays the same, although in a more 'relational' way.

The funny thing about this is the intention to extrapolate to those so called 'regimes' where clocks werent available and still talk about the flow of time, because somehow we like continuity. It is fun to run the film backwards isnt it? If we do so, we can call time the 't' in the metric of the universe and 'smothly' (like x^0) connect with the singularity at t=0 somehow, or talk about baby universe and all that jazz...

The bottom line is that time is not an illusion, is an invention, a parameter in our equations. The magic comes when we map that into the outer world and we repeat experiments many different ways, with different *clocks* and *rods*, and we get the same damn answer. Here one could actually start a discussion on whether the speed of time is a well defined concept (1 second per second ;) ).

All this made us believe there is something beyond our understanding which appears to flow independently of everything. This, as we know ;), isnt true, cus time is what's on the clock (remember, solve for t?), and that's why is relative, and that's why it isnt absolute. And that's what led Einstein to postulate the principle of relativity.

Now, if you pounder why is it possible to be at the same place at two different instants of time, but you cant be at the same time in two different places (well, at least not after you decide to be *somewhere*, if you understand what I mean...). Or why is there a minus in the Minkowskian metric or we like to go Euclidean (to pick funny epsilons), then you are starting to have a point, or at least a more oriented question which could take u surf the electromagnetic wave too :)

One could go on and on, and I could easily argue against myself, besides it is getting a bit late, according to my watch, so I should probably go to bed... :)

Dirac also realized that every particle in our world must have an antiparticle with an opposite charge. This discovery was the seed for the "radiative effects", the "running" of the gauge couplings, and the correlation between the fundamental forces and their unification: in other words, it led physics to the triumph of the Standard Model.

How would you know when you had "time" if you did not add the "i" in the matrice of Dirac.

So how do you know when you have this "cross over" in LHC, or neutrinos that have an oscillatory feature to them? If the "oscillations stop" you have no more particles? Even "empty space" has particles?

How about a vintage terpene solution extracted from the body fluids of an Iguanodon?..the ancient ritual of slurpping dinosaur p*ss, has been handed down to many recent civilizations, though not recommended, it is still practiced, along with a snuff_like derivative used to enhance random_like air walks?

Under ordinary conditions, the orthopositronium constituents—an electron and a positron—produce a specific amount of energy when they annihilate each other. But that energy simply wouldn't be there if the orthopositronium had oscillated into its undetectable mirror form. See here

So what appears as a distraction in relation to time has some interesting features to it. Dirac in his "geometrical thinking and abstractions" helped us to see the dynamics of the universe in a interesting way.

The Pierre Auger Observatory in Malargue, Argentina, is a multinational collaboration of physicists trying to detect powerful cosmic rays from outer space. The energy of the particles here is above 10^19eV, or over a million times more powerful than the most energetic particles in any human-made accelerator. No-one knows where these rays come from.

Such cosmic rays are very rare, hitting an area the size of a football field once every 10 000 years. This means you need an enormous 'net' to catch these mysterious ultra high energy particles. The Auger project will have, when completed, about 1600 detectors. See here

Also,

Special Lagrangian geometry in particular was seen to be related to another String Theory inspired phenomenon, "Mirror Symmetry". Strominger, Yau and Zaslow conjectured that mirror symmetry could be explained by studying moduli spaces arising from special Lagrangian geometry. See here

I have a few more days and then my wife and I will be homeless, :) until we can set "our roots" in the location for building. Anyone know of a way to transmit "cheap" costing information over cell phones for internet connectivity?

I find Wick rotations one of the most mysterious things in qft. The problem I see in GR is that a signature change in addition to the metric being smooth means the determinant (alas 4 - volume) has a zero. I am not sure if one can make sense out of that. There's also a rather weird paper by Wetterich (hep-th/0405223) where he tries to get Lorentzian signatures, but I can't say this makes sense to me either (in addition, I find groups like SO(128, C) a bit unappealing).

Hi Garbage,

Thanks for the concise summary! Say, if you'd think completely classical, then everything is deterministic. Free will is an illusion (in the meaning that everything what you do was determined the day you were born, just that you didn't know). Time, in this context, is an order parameter for events to happen, but if you know the 'now' you know all the past and the future. In this sense, I'd say both exist (I don't care much that there's an arrow of time that makes our brains only recall the past).

Now if you go to quantum mechanics, the past 'is' but the future isn't? Or is it? And if it's not, why is now now and not some other now? And if now is where the future turns into the past, then in whose reference frame (or which slicing)? I mean, shouldn't we all have the same 'now' if there's only one? I think I'm getting a headache.

Whenever I try to understand stuff like this it seems to me we either give up our notion of time, or quantum mechanics. I admit, I'd rather give up quantum mechanics.

Yeah, I think we just found the cause for the alleged crisis in physics. I think I know how to cure that. How about a weakly shroom evening? At the very least our papers would be more... inspired.

Hi Plato,

good luck with the move and everything! Regarding internet: I found it's pretty easy nowadays to find a cafe with a T-mobile hotspot, or better, with an own wireless. If you can, pick a cafe next to an office building during work hours. If you are lucky you'll have a whole bunch of unsecured networks...

"How about this being slightly biased?;;for instance we have all stood infront of a mirror, and when I look into this mirror I see myself "at one instant, in two seperate places"

Jiji, a few remarks. First, it isnt true you see yourself at hte same 'instant' of time, there is some elapsed time between the light traveling back and forth to your eyes and your brain processing the image (this are non trivial observations indeed...) Now, you believe that image and you *are* at two diferent places at the same time, cus you extrapolate once more time, it is easier and our brains like it :)And secondly, unfortunately the one you are looking at is not 'yourself' either, did u try lifting the *left* hand ;)As you may know also, there is the non-clonning theorem in QM, so better stop watching mirrors too closely :D

Hi Bee [ It is funny, my girl ist eine biene auch and I also call her bee ;) ]

"... Free will is an illusion"

Free will is an illusion in any realm!!

The problem with time, and the now, the past and the future, is *our* problem, that is what ibuprofen is for ;)

After some time around these issues you come to realise almost anything can work as *time* and physics is purely relational. There are complementary ways to look at things, there is no absolutes out there!

I think QM is even easier. At the classical level, for something to work as a good time (clock) is has to obey certain properties, like transversality. In the quantum realm (even better withing GR), once everything is equal footing one can construct conditional probabilities and *evolve* them on any physical parameter you wish. One has to be careful with the interpretation, but once we devoid ourselfs of preconceptions, it works just fine. Of course the problem is hiden somewhere else, like in the meaning of states and how do you *prepare* them (the initial value problem). Also if you want to have some fun better chose a good variable to call time.

I agree there is something deeper to struggle with in the notion that 'time goes by' independently of any clock you chose to actually *measure* 'it'. (I ran out of ** and ' ' to scape dwelling into philosophy :) )I also agree that the fiducial spacetime (manifold) is vital in order to construct this relational picture and where does it come from? Is it just as in gauge theories a 'device' to construct meaningful quantities? Then we could argue about emerging topology and so on, but this would make a diverge even more...

There is also the issue of 'measurement' I barely touched upon above, and I think is what bothers you, which is on the heart of the problem too. What about 'reduction', is it 'instanteneous'? Is it physical? does it have to do with us?

My personal way to look at this is that 'measurement' is nothing but more of the same but actually much *more*, and totally independent of us. Nevertheless, there are many different pictures which complement each other whether we decide to look at this in different ways. States are nothing but dispositional states and as such are purely relational objects.

I think any attempt to extrapolate concepts is a dangerous venue, I think this is the best we can do, which is good enough based on the type of langauge and resources we have at the time. I truly believe math is an invention, not a discovery. I biased one though... ;)

Garbage:"And secondly, unfortunately the one you are looking at is not 'yourself' either, did u try lifting the *left* hand ;)"

We are entering Hyperbolic regimes?..the consequence of which can be stated thus,the mirror image is "NOT" isomorphic, lifting my hand proves this?

Now, being it is not my mirror image that asked me to raise my hand, lets say we meet face to face?..lets state that we are 6 ft apart, facing each other, you (A) and myself (B). You proceed to ask me to lift my "left" hand, this I do.

What do YOU see?..as you have replaced the mirror, you see me lifting my RIGHT hand!

I have obeyed your "input" ordering, but it has resulted in a reversed "output" permutation?..are you ok/happy with this?

I have the freewill to obey your command, even though I know it will provide you with an illusionary unrequested effect!

You of course are free to circumvent me in 3-D spacetime in order to rectify the "handwaving" effect, my 2-D mirror image has no such luxury!

"As you may know also, there is the non-clonning theorem in QM, so better stop watching mirrors too closely :D"

I have the answer to this, but it would involve some hefty philosophical quantum "its", along A Seth Lloyd initial state "pre-conditioning" of information paradox's?

P.S In my webpage link on name, it shows Two mirrors, and a polished metal ball rests on one surface, can you see where the image of the ball is "illusionary" ?

Sorry, I meant to state that there is only ONE actual ball in the linked picture, if you rotate (or turn your head side on)..then you can see the basic image that Newton used in early experiments, which I believe set him on the road to understanding motion, and moving bodies, before mirrors were created, polished balls wre the in_thing ;)

I read parts of this paper. It was really helpful to understand some parts of the whole issue. I don't know though why that paper is linked on the qg side, it shouldn't be there. Joy changed the date for his talk, the title is

"Planck Scale Tests of the Principles of Physics with Cosmic Neutrinos"

The time problems I find interesting, but it's nothing I would want to work on. I like to follow the discussions though.

Time may be an illusion, which I believe it is, however, within the society in which we live in ("all of us"), we live with "timed certainty", therefore, unless we fail or reject to live within the limitations of our universal cycle - sun rises, sun sets; then time is strictly a "reality" which we could only wish it was simply just an illusion. Our banks close at what we know as 5pm. The first flight out of the airport is at 6am. The shortest time in which an ambulance can get to us is 7 minutes, and so on. The time the we as humans have created is a field unit, that separates our human capabilities to perform, process and understand. As long as we are trapped in these fleshly vessels of ours, then we "must" obey the simple principles of "our" time. After that, I'm sure is a different story...

You all bunch of nerds trying to be heroic to solve this stupid topic.

Time is a measurement made by mankind jus like we decide to use miles, meters , cm , mm, kg, inches and everything else.

What ever all those fancy nonsence statements mean i dont know but ty n think of it this way.

by the way for that idiot who said bout the one hour change. Well the reason for it. Its because a day has jus a little less than 24 hours a day mater of a second or maybe miliseconds. and thats why we have a loop year too. the time change is also used because of the days get shorter n longer dependig on seasons.

All devices for measuring time rely upon motion over space. Ie, they measure space directly and from that measure we manufacture or infer a measurement of time. Given space and motion, time becomes only a counting of displacements generated by motion over space. Motion is real, space is real. Time is the ghost of dead motions. Or, time is a parameterization of an equation in motion and space. Or, time is an index to motion. Or, time is the order of events consequent upon the action of motion across space. What time is not is an extended dimension. The notion that time is an extended dimension is only a reification from the extended dimensionality of space.